1. Field of the Invention
The invention relates to a motor-driven compressor, and more particularly to a motor-driven compressor to be installed on a vehicle.
2. Description of the Related Art
In a hybrid vehicle that travels by using an engine and an electric motor, the ratio of engine operation mode and electric motor operation mode is changed according to the running state of the vehicle. Where the aforementioned hybrid vehicle is configured such that a compressor that actuates the refrigeration cycle constituting an air conditioner receives drive power from the engine, the compressor cannot receive the required drive power from the engine at all times. Therefore, hybrid vehicles use a motor-driven compressor that is driven by electric power obtained, for example, from a battery installed on the vehicle. The motor-driven compressor is attached to the vehicle body or engine.
However, a hybrid vehicle is sometimes operated only by the electric motor in a state in which the engine is stopped, for example, in an idle reduction mode, and where the motor-driven compressor is operated when the engine is thus stopped, unpleasant noise is generated inside and outside the vehicle due to the operation of the motor-driven compressor. In particular, the main cause of the unpleasant noise is resonance noise generated by vibrations of the vehicle body or engine caused by vibrations of the motor-driven compressor transmitted thereto by the attachment parts of the motor-driven compressor, rather than the noise emitted by the motor-driven compressor itself. Accordingly, attachment structures of the compressor designed to moderate the vibrations transmitted from the motor-driven compressor to the vehicle body or engine have been suggested.
Japanese Utility Model Application Publication No. 564-44810 describes a structure in which a screw is inserted in each through hole of cylindrical mountings attached to a compressor and each screw is screwed into each threaded hole of the attachment body of an engine, thereby mounting the compressor to the attachment body. Further, a vibration-damping rubber is wound about the outer circumferential surface of the cylindrical mounting. In a state in which the cylindrical mountings with the vibration-damping rubber wound thereon are disposed on the inner side of semicircular curl portions of a base mounting, the base mounting is fixed to the outer side of the compressor by screwing and mounting to the compressor. In this case, the vibration-damping rubber is interposed between the base mounting and the cylindrical mounting and between the compressor and the cylindrical mounting.
However, in the compressor described in Japanese Utility Model Application Publication No. S64-44810, the base mounting covered from the outside of the cylindrical mountings is screwed and fixed to the compressor together with the cylindrical mountings, but when the base mounting and the cylindrical mountings are attached to the compressor, the cylindrical mountings and the base mounting should be screwed in a state in which they are disposed and fixed at a predetermined position of the compressor. The resultant problem is that the base mounting and the cylindrical mounting have poor assemblability. Another problem is that in the base mounting that has been fixed by screwing, the screwed joint is loosened by vibrations of the operating compressor and the base mounting and the cylindrical mounting can be separated from the compressor.